Neutralized high frequency amplifier



Dec. 12, 1939.

W. BUSCHBECK NEUTRALIZED HIGH FREQUENCY AMPLIFIER Filed Jan. 29, 1938 INVENTOR W. BUSCH ECK ATTORNEY Patented Dec. 12,1939

Umrs STATE rear 3 OFF! AMPLIFIER NEUTBALIZIED HIGH "FREQUENCY.

tion of Germany Application January 29, 1938, Serial No. 187,751

In Germany February 12, 1937 I 6 Claims.

The invention relates to a further development of the arrangement for neutralizing high frequency amplifiers as described in United States application Nd 177,425 filed December 1, 1937.

, "5. The. subject matterof .the main application is a differential condenser whose stators are connected to the anodes of-the high frequency amplifier tubeand to. the tube imitation or non.- heated tube serving for the neutralizing, and 10, whose center part is placed at the grids of the tubes. In accordance with a further embodiment of this idea shown in the main patent, the center part of the differential condenser is fixed and the plates proper of the tubes serve as stators. The capacitive relationship is varied by Y displaceable shielding walls arranged on both sides of the part connected to the grids and which have ground potential. In accordance with the invention this last mentioned arrangeiio ment is essentially simplified and. improved in that they serve as differential condensers, the

. stray' capacities existing as a result of the exterior tube structure, between the grid and plate of the tube and between the grid and anode of 23 the tube imitation serving for the neutralization, and that these stray capacities are shielded more or less by a grounded, movable conductor.

' Whereas the arrangement described in the main patent can be used primarily in case of smaller tubes, the arrangement according to the invention offers particular advantages. especially when using large tubes in which the stray capacities assume larger values, The grid-plate capacity will in fact not be increased as in the case of the subject matter of the main patent,

but it will even be decreased due to the presence of the shielding while, however, the cathode plate capacity will be increased. The increase in the cathode plate capacityhas an especially favorable effect in the single plate neutralizing circuit in which throughthis measure, energy transferred from the control transmitter to the main transmitter is diminished, so that the load of the control transmitter will be decreased.

As compared with the arrangements already proposed and in which the neutralizing capacity is reduced inside the non-heated tube serving for the neutralizing, the arrangement according to the main patent, as well as that according to the present invention, have the advantage that the danger to be expected from a deterioration in the course of time of the vacuum is eliminated be-- cause the tube and imitation for the neutralizing can be used alternately as operating tube. Furthermore, the rather complicated arrangement to be accommodated in the vacuum can be dis 'pensed with,

An example embodying the idea of the invention will now be described with reference to the accompanying figure. Item, i is the heated tube '5 and 2 is the non-heatedtube or imitation serving for the neutralizing. The tube and imitation are disposed in a straight line and so adapted that the grid and cathode leads thereof designated by G and K extend concentrically to each other and in this straight line. There is arranged about the plate or anode cylinder A, that. is ordinarily water cooled, and connected to A, a metal cylinder M serving as a layer of the condenser of the oscillator circuit, whose other layer is formed by the grounded outer cylinder E. Item L is the coil of the oscillatory circuit. The tube and the imitation for the neutralization are constructed entirely symmetrically. For the fine adjustment of the neutralizing arrangement there is arranged in accordance with the present invention, between the grid connection V and the anode cylinder ,M, a metal cylinder N that, can be moved in the longitudinal direction of the entire arrangement and which is grounded and located in its central position entirely symmet rically to the .tube and the imitation. If, however, it is displaced in the longitudinal direction, it shields the stray capacity between the grid G and the anode enclosing'cylinder M of the 0 tube to a greater degree or lesser degree than the corresponding stray capacity of the imitation so that it is possible to decrease the influence upon the values of the two grid anode intercapacities, .The metal cylinder N may also be re- 35 placed by a simple metal rod or another grounded conducton The conductorN is fastened for instance to a handle that can be moved to and fro across a slot in the shielding cylinder E, and which is conductingly connected to the shielding 40 cylinder. The control energy is applied to the tube arrangement in the center of the entire system between the grid and cathode lead, say between points 8 and It. Item I-I designates the heating chokes which place the cathode ends at 45 ground. v

The invention is not limited to the example of construction shown and can be applied to.al1neutralized tube arrangements in which the stray capacities between the grid and anode of the 50 tube and the imitation are accessible.

I claim:

In a neutralized high frequency wave relay system, an electron discharge tube having an anode, a cathode, and a control grid to which 55 control grid and cathode high frequency wave energy may be applied, a neutralizing capacity substantially equivalent to the capacity between the grid and anode of said tube and arranged in a manner similar to the said electrodes of said tube, a difierential condenser having one stator connected to the anode of said tube, another stator connected to an element of said neutralizing capacity, and a movable element differentially and adjustably movable relative to the said stators between the grid of said tube and one stator and between the remaining element of said neutralizing capacity and the other stator.

2. In an arrangement for neutralizing high frequency amplifier tubes having grid and plate electrodes, a tube capacity comprising interelectrode capacity substantially equal to the grid to plate capacity of the said tube amplifier, connected to neutralize the grid to plate capacity of said first tube amplifier, and means for shielding the stray capacities between the grid and plate of the first tube and between the electrodes of the second tube forming said inter-electrode capacity comprising a conductive member difierentially movable relative to an electrode in said first tube and to an electrode in said second tube.

3. An arrangement as recited in claim 2 wherein the first tube and the second tube serving for neutralization of the first tube are disposed on the same axis and wherein said member 'is a grounded metallic member enclosing the connection between the grid in said first tube and the corresponding electrode in the second tube, said member being movable along the axis of the tube arrangement.

4. An arrangement as recited in claim 2 wherein the first tube and the second tube serving for neutralization are coaxially mounted and wherein the electrodes in said second tube are a grid and an anode and wherein the tubes are surrounded by metallic cylinders connected to the anodes, and wherein the grids are connected by a lead and the member is grounded and located between the said grid lead and the ends of the said metallic cylinders connected to the anodes of the first tube.

5. An arrangement as recited in claim 2 wherein the entire arrangement is enclosed by a grounded cylindrical shield.

6. In a neutralized high frequency relay system, an electron discharge tube having an anode, a cathode and a control grid to which control grid and cathode high frequency wave energy is applied, a neutralizing capacity in the form of a second tube having electrodes between which a capacity exists which is substantially equivalent to the capacity between the grid and anode of the said first tube, a connection between said grid of said first tube and an electrode of said second tube, a high frequency output circuit connected between the anode of said first tube and the other electrode in said second tube, and means for shielding the stray capacity between the anode and grid of said first tube comprising a conductive member coupled to said anode and grid and to said electrodes of said second tube and means for moving said member to differentially vary said couplings.

WERNER BUSCHIBECK. 

